The invention relates to a horse chestnut, or Aesculus hippocastanum, extract. It also relates to a cosmetic composition comprising said extract. It lastly relates to the use of the extract for the cosmetic treatment of the skin and/or mucosa.
The horse chestnut tree (Aesculus hippocastanum) is a large tree reaching up to 30 m tall; it grows quickly, has a robust and straight trunk, and is ball-shaped. The reddish-brown bark stays smooth for a long time, then cracks lengthwise, peels, and detaches in plaques. Its foliage is deciduous. The pointy buds appear in the fall and are protected by a very sticky resin. The leaves are opposite, palmate and large (30 to 50 cm). The inflorescence is made up of white zygomorphic flowers, often with red or yellow spots. The fruit is a green capsule (chestnut husk) with a thick, smooth wall that contains one (sometimes two or three) large, smooth and glossy brown seed(s), known as “chestnut”. This seed is not edible.
The horse chestnut tree is a particularly widely used plant species in cosmetics, dermocosmetics and the pharmaceutical industry.
The use of horse chestnut seed extracts, primarily containing a mixture of triterpene saponins known as aescin (or escin), is known in the prior art in many preparations to treat chronic venous insufficiencies and to relieve certain symptoms, such as heavy and swollen legs. Aescin reduces capillary fragility by inhibiting the hyaluronidase enzyme. Aescin also has anti-inflammatory, antineoplastic, neuro-protective and antioxidant properties. Although many cosmetic preparations include Aesculus hippocastanum seed extracts for their effects on blood circulation, other beneficial effects for the skin are attributed to it as well. An Aesculus hippocastanum seed extract has antioxidant properties greater than those of ascorbic acid and protects the cells from oxidative stress. An Aesculus hippocastanum seed extract causes fibroblast contraction and decreases wrinkles around the eye contours. Document WO2009/107853 A2 for example describes an agent comprising a triterpene saponin obtained by ethanol-water extraction of the Aesculus hippocastanum seeds, which stimulates the contraction of the dermal fibroblasts to prevent and improve wrinkles and skin slackening with age. Aesculus hippocastanum seed extracts improve the protective performance of sun filters. Document WO2009/107853 A2 describes a saponin-rich Aesculus hippocastanum seed extract for an anti-aging effect. This extract is obtained using an alcoholic solvent.
The use of horse chestnut bark extracts is also known in the prior art. Its bark, which has astringent properties, is used to combat diarrhea when taken orally and for antiseptic purposes when applied locally on wounds and ulcers. The bark extracts primarily contain coumarins, such as esculin (or aesculin, or esculoside), fraxin, esculetin and fraxetin, as well as tannins, considered to be vasoprotective and in particular used to treat hemorrhoids, edema.
Document US 2005/048008 A1 describes cosmetic compositions to treat skin aging and to improve skin appearance. This document describes an Aesculus hippocastanum extract, but without specifying the part of the plant from which the extract is obtained. Furthermore, nothing is indicated regarding the nature of the solvent used.
The use of Aesculus hippocastanum flower extract is described in traditional medicine for internal or external use, to treat venous inflammation, varicose veins, hemorrhoids and frostbite. The flower contains flavonoids, and primarily glycosylated derivatives of kaempferol and quercetin. The presence of derivatives of the tannin, coumarin, amine and amino acid type has also been reported. There is also a monograph recorded in the French Pharmacopeia for a homeopathic preparation from Aesculus hippocastanum flowers. In this case, it involves a mother tincture obtained by hydroethanolic extraction (45/55 V/V) of fresh flowers carried out using the general technique for preparing mother tinctures. The MINTEL document (database accession number 3967717) describes a cosmetic composition for treating the skin comprising an Aesculus hippocastanum flower extract. This document does not describe the nature of the solvent used to obtain the flower extract.
For a solvent polarity range comprised between that of ethanol and water, the presence of saponins and/or coumarins may cause a potential toxicity of the extracts, notwithstanding their aforementioned efficacy.
Furthermore, the choice to be made among the available solvents to obtain extracts raises a certain number of difficulties.
Aqueous solvents require the addition of a microbiological preservative to guarantee their stability. Yet the usage field of preservatives is increasingly restricted, in particular due to the required toxicological data. Propylene glycol has proven potentially toxic, and the current trend for manufacturers is to avoid it. Agro-sourced butylene glycol is relatively expensive, which limits its industrial use. Agro-sourced propanediol has the drawback of being derived from genetically modified corn (GMO), which is not readily accepted by consumers, and regarding which some reservations may be wise. Ethanol, although having good extraction power alone or mixed with water, is particularly volatile and flammable, which causes transport and storage problems. Furthermore, due to its drying nature, this solvent may disrupt the hydrolipidic film of the skin and cause irritation for sensitive skin.
Furthermore, plant extracts often being intended to be formulated in cosmetic compositions, it is important to avoid extraction solvents comprising salts or acids, at least trace amounts of which will necessarily be found in the extract. Indeed, it is well known in the prior art that the formulation, as a gel or emulsion, of salt-based ingredients beyond a dose of 0.1% is particularly complex. Furthermore, acids, by decreasing the pH of the obtained extracts, result in making gel or emulsion formulations difficult. In particular, cosmetic products for cutaneous application must have an appropriate pH, preferably close to that of the skin (approximately pH 6.5), or neutral. Under these conditions, the use of solvents containing acids therefore requires the addition of excipients, in particular pH regulators.